The present invention is directed to neuroprotective (antiischemic and excitatory aminoacid receptor blocking) phenol derivatives defined by the formula (I) below; pharmaceutically acceptable salts thereof; pharmaceutical compositions thereof; a method of using these compounds in the treatment of neurological disorders, including anxiety, cerebral ischemia, epilepsy, muscular spasms and stroke; and a method of using these compounds in the treatment of CNS degenerative diseases such as Alzheimer's disease, Huntington's disease and Parkinson's disease. The present invention is further directed to a method of using these compounds in the treatment of drug addiction, migraine and urinary incontinence. The present invention is still further directed to a method of using these compounds in the treatment of traumatic brain injury.
The excitatory amino acids are an important group of neurotransmitters that mediate excitatory neurotransmission in the central nervous system. Glutamic acid and aspartic acid are two endogenous ligands that activate excitatory amino acid (EAA) receptors. There are two types of EAA receptors, ionotropic and metabotropic, which differ in their mode of signal transduction. There are at least three distinct ionotropic EAA receptors characterized by the selective agonist that activates each type: the NMDA, (N-methyl-D-aspartic acid), the AMPA (2-amino-3-(5-methyl-3-hydroxyisoxazol-4-yl)propanoic acid), and the kainic acid receptors. The ionotropic EAA receptors are linked to ion channels that are permeable to sodium and, in the case of NMDA receptors, calcium. Metabotropic receptors, linked to phosphoinositide-hydrolysis by a membrane associated G-protein, are activated by quisqualic acid, ibotenic acid, and (1S,3R)-1-aminocyclopentane 1,3-dicarboxylic acid.
The NMDA receptor is a macromolecular complex consisting of a number of distinct binding sites that gate an ion channel permeable to sodium and calcium ions. Hansen and Krogsgaard-Larson, Med. Res. Rev., 10, 55-94 (1990). There are binding sites for glutamic acid, glycine, and polyamines, and a site inside the ion channel where compounds such as phencyclidine (PCP) exert their antagonist effects.
Competitive NMDA antagonists are compounds which block the NMDA receptor by interacting with the glutamate binding site. The ability of a particular compound to competitively bind to the NMDA glutamate receptor may be determined using a radioligand binding assay. See Murphy et al., British J. Pharmacol. 95, 932-938 (1988). The antagonists may be distinguished from the agonists using a rat cortical wedge assay. See Harrison and Simmonds, British J. Pharmacol., 84, 381-391 (1984). Examples of competitive NMDA antagonists include D-2 amino 5-phosphonopentanoic acid (D-AP5), and D-2-amino-7-phosphonoheptanoic acid, Schoepp et al., J. Neur. Transm., 85, 131-143 (1991).
Antagonists of neurotransmission at NMDA receptors are useful therapeutic agents for the treatment of neurological disorders. U.S. Pat No. 4,902,695 is directed to series of competitive NMDA antagonists useful for the treatment of neurological disorders, including epilepsy, stroke, anxiety, cerebral ischemia, muscular spasms, and neurodegenerative disorders such as Alzheimer's disease and Huntington's disease. U.S. Pat. No. 4,968,878 is directed to a second series of competitive NMDA receptor antagonists useful for the treatment of similar neurological disorders and neurodegenerative disorders. U.S. Pat. No. 5,192,751 provides a method of treating urinary incontinence in a mammal which comprises administering an effective amount of a competitive NMDA antagonist.
NMDA antagonists are also useful therapeutic agents with anticonvulsant, anxiolytic, muscle relaxant, and antipsychotic activity. J. Lehman, The NMDA Receptor, Drugs of the Future, 14, No. 11, p. 1059 (1989). NMDA antagonists have also been reported to be effective for treating migraine (Canadian Journal of Neurological Science, 19(4), p. 487 (1992)); drug addiction (Science, 251, p. 85 (1991)); and neuro-psychotic disorders related to AIDS (PIPS, 11, p. 1 (1990).
Ifenprodil is a racemic, so-called dl-erythro compound having the relative stereochemical formula ##STR2## which is marketed as a hypotensive agent, a utility shared by a number of close analogs; Carron et al., U.S. Pat. No. 3,509,164; Carron et al., Drug Res., v. 21, pp. 1992-1999 (1971). More recently, ifenprodil has been shown to possess antiischemic and excitatory aminoacid receptor blocking activity; Gotti et al., J. Pharm. Exp. Therap., v. 247, pp. 1211-21 (1988); Carter et al., loc. cit., pp. 1222-32 (1988). See also French Patent 2546166. This invention provides compounds possessing such neuroprotective effect in good measure, while at the same time having lowered or no significant hypotensive effect. Additionally, this invention provides compounds with increased metabolic stability so that the neuroprotective effects of said compounds can be enjoyed for a longer period by the patient.
Certain structurally related 1-phenyl-3-(4-aryl-4-acyloxypiperidino)-1-propanols have also been reported to be useful as analgesics, U.S. Pat. No. 3,294,804; and 1-(4-(amino- and hydroxy-alkyl)phenyl)-2-(4-hydroxy-4-tolylpiperazino)-1-alkanols and alkanones have been reported to possess analgesic, antihypertensive, psychotropic or antiinflammatory activity, Japanese Kokai 53-02,474 (CA 89:43498y; Derwent Abs. 14858A) and 53-59,675 (CA 89:146938w; Derwent Abs. 48671A).
Chenard (U.S. Pat. No. 5,185,343 and U.S. Pat. No. 5,272,160) discloses compounds of the formula ##STR3## wherein Q is S or CH.dbd.CH; X is H, OH or another aromatic substituent; R is hydrogen, alkyl, alkenyl or alkynyl; Y and Y.sup.1 are taken together and are arylmethylene or aralkylmethylene (or a corresponding epoxy derivative) or Y and Y.sup.1 are taken separately and Y is hydrogen or OH, and Y.sup.1 is aryl, aralkyl, arylthio, or aryloxy; and structurally related 2-(piperidino)alkanols and 2-(pyrrolidino)alkanols as being useful in the treatment of CNS disorders.
Butler EPO 441,506 discloses 3-piperidino-1-chromanol derivatives having the formula ##STR4## wherein A and B are taken together and are --CH.sub.2 CH.sub.2 -- or A and B are taken separately and are each H; X is CH.sub.2 or O; X.sup.1 is H or OH; Z is H, OH or halo; Z.sup.1 is H, halo or alkyl; n is 0 or 1; and m is 0 or an integer from 1 to 6 as being useful in the treatment of CNS disorders.